Patent Application
20140346272
In general, aircraft landing gear includes a strut connected to the aircraft and receiving a shock absorber. The landing gear also has a landing gear rod designed to penetrate in part inside the strut and to slide therein. The rod is connected firstly to the shock absorber and secondly to an axle-carrier mechanism on which the wheels for enabling the aircraft to run on the ground are mounted.
The rod therefore has a mechanical connection function between the wheels and the aircraft in order to enable the aircraft to run on the ground. The landing gear rod is consequently a mechanical member that is particularly highly stressed during landing since it must withstand the impact of landing, it must carry the aircraft while it is running on the ground, and it must transmit the forces for braking the wheels on the ground in order to enable the aircraft to stop. Consequently, the landing gear rod needs to accept compression forces along the axis of the rod and also bending forces, e.g. during braking.
In order to withstand such forces, landing gear rods are generally made by forging a solid part that is T-shaped or Y-shaped. Forging serves to improve the mechanical strength of the rod. After forging, the T-shaped or Y-shaped rod is bored along a main axis of the T-shape or the Y-shape so as to form a tubular portion suitable for receiving a portion of the telescopic shock absorber and so as to lighten the rod. The bore sometimes extends over more than one meter within the forged part, thereby lengthening production time. The forged and bored part is particularly expensive and complex to make. Making such a part relies on having forging means of large size. For example, a landing gear rod for an aircraft of the Airbus A320® type requires a forged part to be made that is about 1.50 meters long and about 1.20 meters wide. Such a part can be forged only with means that are uncommon and thus expensive.
An object of the present invention is thus to provide a landing gear rod at reduced cost.
In order to achieve this object, the invention provides a landing gear rod for an aircraft, the rod comprising a tubular portion for receiving a shock absorber and an axle-carrier portion situated at the end of the tubular portion and adapted to receive a landing gear wheel support mechanism. This rod is essentially characterized in that the tubular portion and the axle-carrier portion are made of mutually distinct metal materials, the tubular portion being made of a first metal material and the axle-carrier portion being made of a second metal material, the tubular portion and the axle-carrier portion being connected together by at least one weld.
There are numerous advantages in making a landing gear rod by welding together a tubular portion, e.g. made by extrusion, and an axle-carrier portion made of another material such as a material that is forged or a material that is molded and subjected to hot isostatic pressing. In particular, there is no longer any need to bore the rod of the T-shape in order to form the tubular portion. Instead of forming a rod as a single piece, it is made up as a plurality of portions that are made separately from one another prior to being assembled together by welding. By means of the invention, the production means used for producing the rod, such as die-stamping means or isostatic hot press means can be smaller in size than would otherwise be needed if the rod were a single part.
In position, given the local mechanical stresses that need to be withstood by the rod, it is essential for the axle-carrier portion to be particularly strong. By means of the invention, there is no longer any need for the tubular portion of the rod to be made of a material that presents the same strength characteristics as the strong material of the axle-carrier portion. Thus, although in order to impart a high level of mechanical strength thereto the axle-carrier portion needs to be forged or made by hot isostatic pressing of a molded part, these forging or hot pressing operations can be limited to the minimum strictly required, i.e. to the sole portion of the rod that is to receive the wheel support mechanism, and need not concern the tubular portion. The tubular portion is thus not necessarily forged or hot pressed. Specifically, as explained below, the tubular portion is preferably produced by extrusion in order to orient its fibers so as to improve the bending strength of the rod of the invention. Consequently, this tubular portion may be produced with standard section member tubes that are merely cut to length.
In order to satisfy the above-mentioned objects, the invention also provides a method of fabricating a landing gear rod for an aircraft, wherein a welding operation is used to connect together:
the tubular portion and the axle-carrier portion being made of respective first and second mutually distinct metal materials and the axle-carrier portion preferably being made by forging or by hot pressing a molded part.
The invention also provides landing gear as specified above and/or as made in accordance with the method of the invention.
Finally, the invention provides an aircraft characterized in that it includes at least one piece of landing gear of the invention.
The manufacture of the axle-carrier portion of a landing gear rod of the invention is performed by forging operations such as stamping or die-stamping and by a molding operation followed by hot pressing. Even though the tubular portion may also be made by forging, it is generally preferable for it to be made by extrusion.
To understand the present invention, extrusion should not be considered as being a forging operation, where forging consists in die-stamping, and/or stamping, and/or coining, and not extruding.
Other characteristics and advantages of the invention appear clearly from the following description made by way of non-limiting indication and with reference to the accompanying drawings, in which:
a and 1b show the making of a Y-shaped landing gear rod in a first embodiment of the invention;
a and 2b show the making of a T-shaped landing gear rod in an alternative second embodiment of the invention; and
a and 3b show the making of a T-shaped landing gear rod of the invention in an embodiment that is an alternative to that of
As mentioned above, the invention consists essentially in a landing gear rod 1 for sliding at least in part in a landing gear strut (not shown in the figures).
The rod is made by welding an axle-carrier portion 2 made by forging or by molding with hot pressing to a tubular portion 3 or tube 3, preferably by using an annular weld 4.
The forging includes at least one die-stamping operation.
Pressing or hot pressing a molded part (also known as hot isostatic pressing (HIP)) consists in molding a metal part to have the required shape and in placing it in the enclosure of a furnace in which ambient pressure is several hundreds of bars, preferably lying in the range 1000 bars to 1500 bars, and where the temperature is high but without going beyond the melting temperature of the metal material forming the part. Under such conditions, any pores in the molded part disappear in part, thereby improving the mechanical characteristics of the molded part in a manner that is substantially equivalent to what the characteristics would have been if the part had been obtained by forging. Given the pressure and temperature conditions inside the enclosure of the furnace, this technique can be used only for parts of small dimensions. By means of the invention, the portion(s) that are not yet assembled with the rod, such as the axle-carrier portion 2a, 2d, are of dimensions that are compatible with the enclosures of hot press furnaces, thus making it possible to make landing gear rod portions using standard pressurized furnaces. It should be observed that it may be advantageous to mold a part rather than to forge it since molding makes it possible to obtain the required shapes directly, which shapes cannot be obtained directly by forging.
As shown in
The tubular portion 3 extends between the weld 4 and the first end 1a.
The axle-carrier portion 2 extends between the weld 4 and the second end 1b.
The landing gear includes a shock absorber (not shown in the figures) that is deigned to penetrate into the strut and bear against the landing gear rod 1, and to penetrate at least in part inside the tubular portion 3. It should be observed that under certain circumstances, the tubular portion 3 may act as the piston of a shock absorber, with the cylinder of the shock absorber then being constituted in the strut. The shock absorber serves to damp the sliding movements of the landing gear rod inside the landing gear strut.
The strut is designed to be assembled to the aircraft, and the axle-carrier portion 2 is designed to receive a landing gear wheel support mechanism. This landing gear wheel support mechanism is not shown in the figures, but it may be constituted:
The landing gear rod of
In order to make a straight landing gear rod in accordance with the various embodiments of the invention and providing an interface between the strut, the shock absorber, and the landing gear wheel support mechanism, a tube 3 is used for constituting a shank, together with one or more parts 2a, 2b, 2c, 2d, 2e, 2f, 2g that have been forged or molded and then hot pressed. These parts 2a, 2b, 2c, 2d, 2e, 2f, 2g constitute the axle-carrier portion 2. These (forged/die-stamped or molded and hot pressed) parts have the feature of being short in length compared with the length of the tubular portion 3. Such die-stamped parts 2a, 2b, 2c, 2d, 2e, 2f, 2g of the axle-carrier portion 2 can be made using die-stamping or hot press means that are small in size compared with the die-stamping means that are needed for making a single piece landing gear rod of equivalent size, by die-stamping or molding and hot pressing.
As explained below, given that the rod is made by welding together a plurality of portions, the materials constituting it may be selected so as to obtain characteristics that are optimized for each zone of the rod 1.
Thus:
The first material of the tubular portion 3 is consequently selected for its ability to bend without breaking and/or for its light weight and/or for its ability to avoid buckling under the effect of the impact of landing, whereas the second material of the axle-carrier portion 2 is selected for its ability to withstand traction and/or compression and/or corrosion.
By way of example, if it is desired to obtain a lightweight landing gear rod having good resistance against corrosion, the first material should be an aluminum alloy that is light in weight, while the second material should be titanium alloy that is relatively insensitive to corrosion.
On this topic, it should be observed that the landing gear rod that is the most sensitive to corrosion is situated at the level of the axle-carrier portion 2 that is closest to the ground and consequently that is the most likely to receive projections of chemicals such as runway antifreeze or impacts from pieces present on the ground such as stones.
The invention also makes it possible to act on the orientation of the fibers of the rod.
Thus, since the tubular portion 3 is preferably made by extruding a first material along an extrusion axis, the fibers of the tubular portion 3 are oriented parallel to one another and to the longitudinal axis X-X. The tubular portion 3 as obtained in this way possesses greater capacity for bending while having a reduced risk of breaking on impact, compared with a forged part.
Furthermore, since the axle-carrier portion 2 is welded to the end of the tubular portion 3, the fibers of the tubular portion 3 are then oriented in the same direction relative to said forged axle-carrier portion 2. The work of designing a strong landing gear rod is thus made easier since the orientation of the fibers in the tubular portion 3 in the vicinity of its zone of contact with the axle-carrier part 2 is known exactly. This would not be true if the rod were made as a single die-stamped part, since the die-stamping would have the effect of deflecting at least the surface fibers of the rod.
In the invention, the respective shapes of the axle-carrier portion 2 and of the tubular portion 3 may be designed so that in the vicinity of the contact zone Z between the tubular portion 3 and the axle-carrier portion 2 and prior to welding, the majority of the fibers (both the fibers of the tubular portion 3 and the fibers of the axle-carrier portion 2 in the vicinity of the contact zone):
It should be observed that the first material forming the tubular portion 3 is generally extruded by pushing this material in the ductile state through a die so as to form simultaneously a hollow zone inside the first material while it is being extruded. The tubular portion 3 is produced merely by extrusion without there being any need to bore a forged part in order to form the tube. This saves an operation of boring a forged part which until now has been particularly expensive in terms of time and material.
In the Y-shaped embodiment of the rod as shown in
These projections 2a and 2b, which are in the form of plates, are spaced apart from each other so that when they are assembled they form a Y-shaped fork, as shown in
Each projection 2a, 2b presents its own bore 6a, 6b extending along a transverse axis Z-Z perpendicular to the longitudinal axis X-X of the tubular portion 3.
As mentioned above, this Y-shaped fork enables a rocker bar of the landing gear wheel support mechanism, specifically a truck, to be mounted in a fork. This rocker bar passes between these projections 2b and 2c and pivots about a transverse pivot (not shown in the figures) that extends along the transverse axis Z-Z inside the bores 6a and 6b of the projections 2b and 2c.
The Y-shaped landing gear rod 1 is thus made up of:
It should be observed that in order to form the Y-shaped fork, it is possible, as in the example of
These lateral portions 2b, 2c are preferably welded to the central portion 2a by friction welding.
As an alternative to this embodiment of
It should also be observed that the friction weld 4 between the tubular portion 3 and the axle-carrier portion 2a is preferably made by establishing relative rotation between the axle-carrier portion 2a and the tubular portion 3. The parts 2b and 2c are welded to the part 2a after making the weld 4.
It should also be observed that friction welding the central portion 2a of the fork (
The advantage of friction welding is that it gives rise to diffusion of atoms at the interface between the welded-together parts, so the quality of the bond as obtained in this way is better than the quality of the welded materials themselves. There is no need to provide any filler metal, which means that it is possible to weld together materials that are different. The welds used for making the rod of the invention and for performing the method of the invention are preferably inertial, linear, or orbital friction welds making it possible to conserve the properties of the forged materials and the properties of the materials forming the tubular portion that is to receive the shock absorber.
By way of illustration, landing gear having a fork-shaped landing gear rod for mounting a rocker bar in the fork is described in patent document GB 2 474 686. In that document, the landing gear rod carries a wheel support mechanism that is a truck in which the rocker bar pivots on a transverse pivot passing through the bores in the projections. The rod of that prior art landing gear is a single piece and it could advantageously be replaced by the landing gear rod of
In the embodiment of the rod shown in
In the embodiment of
Ideally, and as can be seen in
Two rings 2e and 2f are respectively welded concentrically around the shaft 2d of the axle-carrier portion 2. These rings 2e and 2f are arranged symmetrically on either side of the axis X-X and they form fastener rings for brake stators of the landing gear.
The brake rings or collars 2e, 2f are preferably welded by inertial friction welding on the axle-carrier bar. Holes are made through these rings for passing brake-fastener studs.
In an alternative embodiment, not shown in the figures, it is also possible for the axles to be formed by a transverse bar that is distinct from the axle-carrier portion 2, the transverse bar being for example engaged in a bore formed in the axle-carrier portion and extending along the axle axis perpendicularly to the longitudinal axis of the tubular portion.
Another embodiment of a T-shaped rod is shown in
The central portion 2g may be made by forging or molding and hot isostatic pressing. The axles 2h, 2i are tubes formed by extrusion or by molding and hot pressing or possibly by forging. These axles 2h, 2i are welded to the central portion 2g by orbital friction. This embodiment serves to reduce the size of the parts forging the rod since, unlike the embodiment of
| Number | Date | Country | Kind |
|---|---|---|---|
| 1161292 | Dec 2011 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/074712 | 12/6/2012 | WO | 00 | 6/5/2014 |
